This invention relates to a test device for checking a pre-vacuum steam sterilization apparatus.
The technical field of the invention is that of the production of test devices capable of checking the quality of the sterilizing gas such as steam in a pre-vacuum apparatus intended for sterilization with said steam, and in which it is therefore desirable to determine the efficacy of the vacuum produced before introducing said steam, and then the quality of the latter once introduced into the chamber.
This invention is intended in particular for tests of pre-vacuum and steam sterilization apparatuses such as, but not exclusively, autoclaves used to sterilize medical and hospital equipment.
The so-called BOWIE-DICK test method has been known since 1961 and has been the subject of various publications, and it is therefore unnecessary to explain it in this application: reference can be made to various prior patent applications that refer to this method, such as application U.S. Pat. No. 4,579,715 published on Apr. 1, 1986 by the WARNER LAMBERT Company or U.S. Pat. No. 4,486,387 published on Dec. 4, 1984 by the PROPPER MANUFACTURING Company or even that of the MXM Company filed on Oct. 20, 2005 and published under number FR 2 892 309, on which this introduction is largely based.
It will simply be noted that the objective of this test is to verify that there is no longer any undesirable gas, in this case non-condensable, in the chamber of the sterilizing apparatus: for this, an ink sensitive to the sterilization gas is generally used, such as a chemical composition sensitive to moisture, but not to the undesirable gases, and placed according to various patterns on a measurement sheet slid inside a pack of porous material or in a hollow receptacle closed at one end and open at the other; said receptacle or pack is placed in the sterilization apparatus during a test cycle that is performed, up to 134° C., at a predetermined frequency, before said apparatus is used to sterilize equipment. Such a test, of which the result is therefore verified after being removed from the apparatus, thus makes it possible to ascertain that there were no more undesirable gases such as air in the chamber, because these gases could become stratified, create pockets of which the temperature could not be controlled, or become mixed with the sterilizing gas, thereby adversely affecting the quality of the sterilization: if the test is positive, i.e. the sensitive ink changed color over the entire surface of the pattern, it can be deduced that there were no undesirable gases during the test cycle and that the same will be true during subsequent equipment sterilization phases.
Various patent applications have been filed to protect various aspects of test devices, including those cited above and, also, among those with a receptacle in the family to which the present invention belongs:                U.S. Pat. No. 6,630,352, published on Jul. 1, 1999 by the 3M INNOVATIVE PROPERTIES COMPANY, which describes and claims a complex device with a vertical receptacle of which the opening faces downward and is surrounded by an external radiator for removing the heat contained in the chamber of the receptacle, which is free of any load and which includes two temperature sensors located against and outside it so as to measure the temperature at two points on the wall;        U.S. Pat. No. 5,066,464, published on Nov. 19, 1991 by the PROPPER MANUFACTURING COMPANY, INC, which describes and claims a device also including a receptacle but arranged horizontally, in which the cross-section of the opening is larger than that of the closed end, in which the chamber of said receptacle includes a heat dissipater formed by a large non-woven “field” sheet “stuffed” by hand into said chamber in order to condense the vapor, and a chemical indicator that is sensitive to moisture such as by changing color, and arranged toward the closed end of the chamber of the receptacle.        
These two examples of embodiments describe the same principle of air/steam separation by progression and condensation along a receptacle with heat dissipation devices in order to condense the steam and thus concentrate undesirable gases such as air, which are in the form of radiators placed outside the chamber or in the form of filling loads placed inside, and with a measuring device that is either electronic and placed outside or that is chemical and placed inside.
The problem stated and not completely solved by any of the documents known from the prior art is that of obtaining results that are reliable and as satisfactory as possible, that of not having to use a test pack that must be opened after use, as in the solution of the patent of the MXM Company, FR 2 892 309 cited above, and, finally, that of simplifying the test devices with a receptacle such as that of U.S. Pat. No. 6,630,352 of the 3M INNOVATIVE PROPERTIES COMPANY, cited above, even if the electronic sensor solution is easier to use than the chemical devices such as that of the U.S. Pat. No. 5,066,464 of the PROPPER MANUFACTURING COMPANY INC, of which the chemical indicator must be removed in order to verify the state afterward, and of which the results are associated with the operator's interpretation of the colorimetric change.